Mechanical hammer



Jan. 20, 1959 J. MRRIS MECHANICAL HAMMER 2 Sheets--SheeI Filed March 5, 1956 Tw/enrol?.

Jarh- 20, 1959 J. MoRRls 2,859,374

MECHAN I CAL HAMMER Filed'MaI-ch 5, 1956 2 shelats--sruewu 2 Ma@ I' ,1W/f6.3

1Q Maf" 11"# United States Patent O MECHANICAL HAMMER Joseph Morris, Los Angeles, Calif.

Application March 5, 1956, Serial No. 569,440

19 Claims. (Cl. 74-22) The presentinvention relates in general to a rotary mechanical hammer and this application is an improvement on the structure shown in my copending application Serial No. 529,815, filed August 22, 1955, reference to whichis hereby made.

The mechanical hammer of the present invention may be utilized for simultaneously reciprocating and continuously rotating a wide variety of tools, such as drills, riveting heads, impact wrenches, and the like, or it may be utilized to operate various devices requiring vibratory power, such as vibrating pumps, for example. While not limited thereto, the present invention finds particular utiiity in the drilling of brick, concrete, rock, or similar materials, the hammering action applied to a drill by the invention, coupled with the rotary motion imparted to the drill thereby, resulting in phenomenally high drilling rates in such materials.

Considering the present invention more specifically, it contemplates a mechanical hammer which includes a housing having therein stationary and movable cam members, the movable cam member being rotatable about and reciprocable along the axis of the cam members. Interengageable, circumferentially spaced cam elements projecting from cam surfaces on the two cam members produce reciprocatory movement of the movable cam member in response to rotation thereof, rotation of the movable cam member being produced by a drive means connected to one end of a shaft on which the movable cam member is mounted. The desired tool or device is connected to the other end of this shaft so that the rotational movement of the shaft produced by the drive means, and the reciprocatory movement of the shaft resulting from the interaction of the interengageable cam elements on the two cam members, are transmitted to the tool. With this construction, the movable cam member and the shaft on which it is mounted are axially displaced periodically in a manner to produce sharp, hammering blows at the tool connected to such shaft, which is an important feature of the invention.

An important object of the present invention is to provide a mechanical hammer of the foregoing character wherein the cam elements projecting from the cam surface of ,at least one of the cam members are rotatable cam elements, such as balls, rollers, or the like, disposed in circumferentially spaced cavities which have substantially flat bottom walls and which have side walls substantially perpendicular to such bottom walls.

In other words, an important object of the invention is to provide cavities and rotatable cam elements which, when viewed in cross section, are square and circular, respectively.

Another important object of the invention is to provide a mechanical hammer wherein the cam surfaces of both the stationary and the movable cam members are provided with circumferentially spaced cavities therein which are square in cross section and which contain rotatable earn elements, such as balls, rollers, or the like, of eir-` ICC cular cross section, the cam elements in the cavities in the movable cam member being engageable with the cam elements in the cavities in the stationary cam member to produce reciprocatory movement of the movable cam member in response to rotation thereof.

An important advantage of the foregoing is that, by utilizing cam elements of circular cross section in cavities of square cross section, there is substantially no tendency for the cam elements to climb out of the cavities as they rotate therein. In other words, since the cavities are provided with side walls which are substantially perpendicular to the bottom walls thereof, the cam elements of circular Cross section are unable to obtain sufficient purchase on the side walls of the cavities to tend to climb out of the cavities to any appreciable extent, as compared, for example, to cam elements of circular cross section in cavities having merging bottom and side walls of semicircular cross section.

The foregoing lack of any tendency for the cam elements to climb out of the cavities-as they rotate therein attains two important new results. First, the reciprocatory impulses imparted to the movable cam member by the interengagement of the cam elements carried by the stationary and movable cam members are perfectly constant, there being no tendency for the reciprocatory impulses to vary in amplitude or magnitude since the cam elements remain in predetermined positions in their respective cavities. Secondly, the controlled interengagement of the cam elements carried by the two cam members, resulting from maintaining the cam elements in predetermined positions in their cavities, substantially eliminates, or at least greatly minimizes, any tendency for'fatigue failures, such as those due to metal crystallization, to occur.

Another object of the present invention in connection `with the preferred embodiments thereof is to provide a mechanical hammer wherein the cam elements carried by one of the cam members are spherical balls disposed in. fiat bottomed, cylindrical cavities of square cross section, and wherein the cam elements carried by the other of the cam members are radially arranged rollers disposed in elongated, flat bottomed cavities of square cross section. With this construction, as the balls and the roller interengage to produce the desired hammering action, no side loads are applied to either the balls or the rollers, thereby minimizing the impact forces applied to the balls and the rollers, and also preventing the development of radial loads on the bearings for the shaft carrying the movable cam member. Such minimizing of the impact forces applied to the balls and rollers further tends to eliminate fatigue failures due to metal crystallization, or other causes, which is an important feature. Another advantage of utilizing interengaging balls and rollers is that the amplitudes of the reciprocatory impulses imparted to the movable cam member are constant irrespective of whether the balls engage the rollers on center, or off center.

Another important object of the invention is to provide a hammer wherein the shaft which carries the movable cam member extends axially through the stationary cam member and is journaled in bearings respectively carried by the housing on opposite sides of the two cam members. With this construction, the rotatable and reciprocable shaft and the cam member carried thereby are supported in a positive manner to minimize wear and the possibility of fatigue failures.

Another object is to provide a housing adapted to contain a lubricant, such as oil, and to provide means for circulating the lubricant past the various moving parts and throughout the housing bothto lubricate the moving parts and to carry heat therefrom to the housing, the latter being provided with heat dissipating fins.

Another object is to provide a lubricant circulating means which includes lubricant scooping ports extending from the periphery of the movable cam member to the cavities therein and facing in the direction of circumferential movement of the movable cam member upon rotation thereof, whereby lubricant from the interior of the housing is scooped into the cavities in the movable cam member to circulate lubricant over the cam elements in such cavities and the cam elements in the cavities in the stationary cam members, both for lubrication purposes and for cooling purposes.

Another object of the invention is to provide pumping means for circulating the lubricant over the moving parts and throughout the housing. Another object in this connection is to provide a pumping means which comprises spiral grooves in journal bearings for the shaft on opposite sides of the stationary and movable cam members. A further object in this connection is to provide a shaft for the movable cam member which is hollow and which communicates with the interior of thehousing at two axially spaced points, and to provide pumping means within the hollow shaft between such points and operable in response toreciproeatory movement of the hollow shaft for circulating the lubricant through the hollow shaft and the housing to lubricate and cool the various moving parts.

Another object of the invention is to provide a hammer which includes a drive shaft telescopically related to the shaft which carries the movable cam member, and to provide, connecting means between the two shafts comprising floating drive pins extending through transverse openings in one of the shafts into longitudinal grooves in the other. With this construction, rotation of the drive shaftistransmitted to the shaft carrying the movable cani member whilepermitting the latter shaft to reciprocate freely without binding, despite vibration, minormanufacturing inaccuracies, and the like.

Another object of the invention is ,to provide a rotary mechanical hammer which may be manufactured readily and economically with a minimum of machining of the various components thereof. In this connection, an object of the invention is to provide a shaft for the movable cam member which comprises two parts respectively threaded into opposite sides of the movable cam member. Another object is to provide a housing which includes an internally threaded and externally inned barrel into the approximate center of which the stationary cam member is threaded, the journal bearings on opposite sides of the stationary and movable cam members being retained by heads respectively threaded into Athe ends of the internally threaded barrel. With this construction, a very simple hammer, the components of which may be manufactured readily and economically, results, which is an important feature of the invention.

The Yforegoing objects, advantages, features'and new results ofthe present invention, together with various other objects, advantages, features and newresults thereof which will be apparent to those skilled in this art in the light of the present disclosure, may be attained with the exemplary embodiments of the invention which are illustrated inthe accompanying drawings and whichA are described in detail hereinafter. Referring to the drawings:

Fig. l is a longitudinal sectional View of the presently preferred embodiment of the rotary mechanical hammer of the invention;

Figs. 2, 3 and 4 are sectional views respectively taken along the arrowed iines 2 2, 33 and 4--4 of Fig. l;

Fig. 5 is an enlarged, fragmentary sectional View taken along the arrowed line 5-5 of Fig. 3 and illustrating the respective circular and square cross sections of VVcam elements and cavities therefor of the invention;l

Fig.A V6 is'an enlarged, fragmentary sectional .viewiltus trating lubricant scooping ports incorporated in the movable cam member of the invention;

Figs. 7, 8, 9, l0 and ll are enlarged, fragmentary sectional views illustrating various other cam member and cam element embodiments of the invention;

Fig. 12 is a sectional view taken along the arrowed line 12-12 of Fig. 1l; and

Fig, 13 is an enlarged, fragmentary sectional view illustrating still another cam member and cam element embodiment of the invention.

Referring particularly to Figs; l. to 5 of the drawings, the numeral 29 designates a hammer housing of the invention which includes an internally threaded barrel 22 provided with external, longitudinal ribs or ns 24 for heat dissipation and provided with a transparent window 26 through which the level of oil, or other lubricant. within the housing may be observed. Threaded into the barrel 22 to a point intermediate the ends thereof is a stationary cam member 2?l having the form of a heavy disc; As will be described in detail hereinafter, interengageable cam elements 3f) and 32 respectively carried by the stationary cam member Z8 and an adjacent, movable cam member 34 cooperate to reciprocate the movable cam member axially of the barrel 22 in response to rotation of the movable cam memberabout the barrel axis. The movable cam member 34, which is also a relatively heavy disc, is fixed on a rotatable and reciprocable hollow shat't 36, they position of the movable cam member axially oi' this shaft being fixed by making lthe shaft in two parts 38 and 40 respectively threaded into opposite ends or sides of the movable cam member and seated against opposite sides'of an internal annular angc thereon. This construction also minimizes machining 'of the various parts of the assembly formed by the ymovable cam member 34 and the shaft 36, which isan important feature.

The part 40 of thecam member shaft 36 projects axially from thehousing 20 through a'journal bearing 42 pressedinto an annular head44 threaded into the corresponding'end of the barrel 22, the head' 44 being pro-- vided-with an lannular ange 46 which .seats on the correspending end of the barrel. The journal bearing 42 is provided with an internal helical groove 48 therein for circulating a lubricant, such as oil, in the housing 20 between the part 40 of the shaft 36 and this bearing. Leakage of lubricant from the housing 20 along the part 46 of the shaft 36 is prevented by an annular seal 50 carried by a gland 52 threaded into a counterbore 54 in the head 44. The outer'end of the part 40 of the shaft 36 is closed by a plug 56 threaded thercinto, and is externally threaded, at S8, for connection to a tool 60, such asa drill, to be simultaneously reciprocated and continuously rotated in response to rotation of the shaft 36 and the `movable cam member 34 .relative to the stationary cam member.28.

The other part 38 ofthe shaft.36 projects axially through .the stationary cam rmember 28'and is v.rotatable and reciprocable n.a-journal bearing ,62'which is pressed'l into and extends through the stationary cam member 28, the bearing 62 having an external 'annular shoulder seated on an internal annular shoulder on the stationary cam member. The journal bearing 62 is also pressed into an annular vhead .64 which is axially spaced from the stationary cam member 28.'an'd which is 'threaded into the opposite end of the barrel l22 from the head'44,'the head 64 being provided with an annular flange 66 which is seated against. the vcorresponding 'end of the barrel 22 tolimit threaded Vinsertion of suchhead into the barrel. An annular spacer 68 encircling the journal bearing 62 between'the head 64`and the stationary cam member 2S serves to fix the axial location of the stationary cam member 28 within the barrel 22. The journal bearing 62 is provided'with an internal helical groove 70 for circulating oil, or other lubricant, between this bearing and the .part38 of the shaft 36.

It will. bev noted' that, Cwith .the-foregoing construc-I tion.. the shaft-36- carrying ,-the'movable .cam member .34

` projects through the stationary cam member 28 and is journaled in the two bearings 42 and 62 respectively located on opposite sides of the Stationary and movable cam members. With this bearing and cam member arrangement, the shaft 36 and the movable cam member 34 thereon are positively supported in a manner to minimizebearing and shaft wear despite the combined rotational and reciprocatory movement of the shaft 36 and the cam member 34, which is an important feature of the invention.

Considering the manner in which the shaft 36 is driven to rotate the movable cam member 34, I prefer to employ a motor 72, such as an electric motor, the housing of which is provided with an axial boss 74 threaded into a counterbore 76 in the annular head 64. With this construction, the motor 72 and the hammer of the invention become an integral unit so that the tool 60 may be manipulated by manipulation of the motor by means of handles, not shown, thereon. The motor shaft, identified by the numeral 7S, is threadedly connected to a drive shaft 80 which is sealed relative to the annular head 44 to prevent lubricant leakage by means of an annular seal 82. The drive shaft 80 is telescopically related to the cam member shaft 36, as by extending into a counterbore 84 in the part 38 of the shaft 36. In -order to transmit rotation from the drive shaft 80 to the shaft 36 while permitting reciprocatory movement of the shaft 36 relative to the drive shaft 80, the drive shaft is provided with transverse openings or bores 86 therethrough for floating drive pins 88 having hemispherical ends which extend into longitudinal grooves 90 of circular cross section in the part 38 of the cam member shaft 36. With this construction, the floating drive pins 88 transmit rotation of the drive shaft 80 to the cam member shaft 36 while permitting the cam member to reciprocate freely relative to the drive shaft without binding, which is an important feature of the invention.

Considering now the manner in which the interengageable cam elements 30 and 32 reciprocate the cam member 34 and its shaft 36 in response to rotation thereof, the cam members 28 and 34 are respectively provided with cam surfaces 92 and 94 which extend generally transversely of the axis of the hammer of the invention, these surfaces being parallel and perpendicular to such axis in the particular construction illustrated. The cam elements 30 and 32 are disposed in circumferentially spaced cavities 96 and 98, respectively, in the cam surfaces 92 and 94, respectively. Preferably, the cam elements carried by one of the cam members 28 and 34 are spherical balls and the cam elements carried by the other are cylindrical rollers, these cam elements projecting from their respective cavities for interengagem-ent as the cam member 34 rotates relative to the cam member 28 to produce reciprocatory movement of the cam member 34. In the particular construction illustrated, the cam elements '30 carried by the stationary cam member 28 are the rollers and the cam elements 32 carried by the movable cam member 34 are the balls, but it will be understood that this arrangement may be reversed. An important feature of this ball-over-roller arrangement, or roller-over-ball arrangement, is that the ball-roller interengagement results in a perfectly constant reciprocation amplitude or magnitude for the Vcam member 34 regardeliminates or at least greatly minimizes fatigue failuresk ofthe various components, due to metal crystallization, v

or. other causes.

Another important feature of the invention is that the cavities 96 and 98 are of square or rectangular cross section in planes parallel to the hammer axis, as best shown in Fig. 5 of the drawings. In other words, the cavities 96 and 98 respectively have substantially flat bottom walls 100 and 102 and respectively have side walls 104 and 106 which are substantially perpendicular to the respective bottom walls thereof, again as best shown in Fig. 5 of the drawings. The cavities 98 for the balls 32 are fiat bottomed cylindrical cavities to provide the substantially flat bottom walls 102 and to provide cylindrical side walls 106 substantially perpendicular to the bottom walls thereof. The cavities 96 for the rollers 30 are radially oriented, elongated cavities the inner ends of which are defined by the outer surface of the journal bearing 62 and the outer ends of which are dened by the outer wall of an annular groove 108 in the cam surface 92 of the stationary cam member 28. With this construction, the roller cavities 96 may be formed very simply by milling, or otherwise forming radial slots in the cam surface 92 between the annular groove 108 and the central opening through the stationary cam member 28 for ease in manufacture.

As hereinbefore outlined, an important result of making the roller and ball cavities 96 and 98squarish in cross section in planes parallel to the hammer axis is that any tendency of the rollers and balls 30 and 32 to climb out of their respective cavities as they rotate, due to frictional engagement between the rollers and balls and the respective side walls 104 and 106, is eliminated, or at least greatly minimized, since the rollers and balls cannot obtain any great purchase on the corresponding side walls. Consequently, reciprocatory impulses of perfectly constant magnitude are assured, whichis an important feature of the invention. Another important feature is that, since the rollers and balls 30 and 32 have virtually no tendency to climb out of their respective cavities as they rotate therein, crushing forces between the balls and rollers are greatly minimized with the result that fatigue failures, due to metal crystallization, for example, are eliminated, or at least greatly reduced.

Preferably, the rollers 30 project from their respective cavities 96 farther than the balls 32 project from their respective cavities 98. With this construction, when the balls 32 are out of engagement with the rollers 30, the rollers engage the cam surface 94 of the movable cam member 34 to prevent engagement between the balls 32 and the cam surface 92 of the stationary cam member 28. Thus, there is band engagement between the rollers 30 and the cam surface 94, instead of line engagement between the balls 32 and the cam surface 92, to minimize cam surface wear. The distance which the balls 32 project from their cavities 98 determines the amplitude 'of the reciprocatory motion imparted to the cam member 34 and its shaft 36 with this construction, and this amplitude may be any desired amount. For example,'in a hammer of the invention designed for use with hand operated drills for drilling such materials as brick, concrete, rock, and the like, a reciprocatory amplitude of from 0.020 inch to 0.025 inch is Satisfactory and pro-- duces extremely high drilling speeds. However, it will be understood that the amplitude of reciprocatory motion may be varied within wide limits, depending upon the' size of the equipment and the purpose for which it is to be used.

Considering now the matter of lubrication of the various components of the hammer of the'invention and dissipation of heat therefrom, the helical lubricant grooves 48 and 70 operate with a pumping action in response to rotation of the shaft 36 in the bearings 42, and 62. Thisy pumping action produces substantial lubricant' circulation through the bearings and throughout the entire housing 20 to carry heat to the externally finned barrel 22 for dissipation by the ns 24. In order to permit lubricant circulation past the intel-engaging rollers and balls 30- and 32, the movable cam member 34 may be provided with generally longitudinal ports 110 therethrough which communicate with the ball cavities 98. Consequently, as the lubricant circulates throughout the housing 2t), it also circulates past the interengaging rollers and balls and 32 to lubricate them and to carry away any heat generated as the result of the roller and ball interengagement.

The embodiment of the invention illustrated in Figs. 1 to 5 of the drawing provides an additional pumping means 112 within the hollow shaft 36 and responsive to reciprocatory movement thereof for producing additional lubricant circulation throughout the housing 28 and over the various moving parts of the hammer. The pumping means 112 merely comprises a plug 114 pressed into the hollow shaft 36 and provided with a passage 116 therethrough adapted to be alternately opened and closed by a flap valve 118 as the shaft- 36 is reciprocated, the flap valve being movable on pins 120. As will be evident, when the shaft 36 is displaced downwardly, as viewed in the drawing, due to interengagement of the rollers 30 and the balls 32, the inertia of the ap valve 118 and the inertia of the lubricant within the hollow shaft causes the flap valve to unseat to permit a small charge of lubricant to flow upwardlythrough the passage 116. Conversely, as the shaft 36 moves upwardly due to the pressure applied to the end of the tool 60, the inertia of the flap valve 118 and the inertia of the lubricant thereabove causes the fiap valve to close to pump lubricant upwardly through the hollow shaft.

The lubricant discharged by the pumping means 112 flows axially through the shaft 36 and escapes from the outer end of the part 38 thereof throughfthe longitudinal grooves in which the drive pins 88 are disposed. rhe lubricant then flows through the helical groove '78 in the journal bearing 62 and out through ports 122 and 124 in the bearing 62 and the spacer 68, respectively, into the interior of the housing 20 on one side of the stationary cam member 28. The lubricant then flows downwardly through longitudinal ports 126 in the stationary cam member 28 into the interior of the housing 20 on the opposite side of the stationary cam member. Then, the lubricant fiows through ports 128 in the annular head 44 into a space between this head and the gland 52, and reenters the shaft 36 on the inlet side of the pumping means 112 through one or more ports 130 in the hollow shaft. Thus, as will be apparent, continuous lubricant circulation throughout the entire hammer is provided to lubricate the various moving parts and to carry heat therefrom to the interior surface of the barrel 22 for dissipation by the external fins 24. It will be noted that the device may be filled with lubricant by removing the plug 56 in the outer end of theA port 4G of the hollow shaft 36.

To increase the lubricant ow over the interengaging rollers and balls 30 and-32, the, movable cam member 34 may, as illustrated in Fig. 6 ofthe drawings, be provided with lubricant scooping ports 132 extending from the periphery of the cam member 34 to the ball cavities 98 and facing in the direction of circumferential movement of the periphery of the movable cam member, the ports 122. in this cam member preferably being omitted under such circumstances. With this construction, the ports 132 scoop up the lubricant in the housing 20 as the cam member 34 rotates and force relatively large steady streams of the lubricant into the ball cavities 98 to bathe the balls 32 and rollers 30 in lubricant for lubricating and cooling purposes, which is an important feature.

Considering now the embodiments of the invention illustrated in Figs. 7 to 1,3 of the drawings, these embodiments include cam members which differ in minor respects from the cam members 28 and 34 and which are provided with different interengageable cam elements. If desired, .except forthe. differences. in the, vinterengageable cam elements., the cam. members; illustrated in:Figs.,7 to 13 Clt of the drawings may be substantially identical to the cam members 28 and 34.

Referring first to Fig. 7 of the drawings, the numerals and 142 respectively designate stationary and movable cam members respectively having cam surfaces 144 and 146 extending generally transversely of the axis of rotation of the movable cam member. The cam surfaces 144 and 146 are respectively provided with cavities 148 and 150 therein which are also squarish in cross section in planes parallel to the axis of rotation, the cavities 148 containing balls 152 and the cavities 150 containing tapered rollers 154. The surfaces of the tapered rollers 154 which are engaged by the balls 152 make acute angles with the axis of rotation of the cam member 142 to produce radial force components, upon interengagement of the balls 152 and the rollers 154, tending to center the cam member 142 relative to the cam member 140. In all other respects, the embodiment of Fig. 7 of the drawings is similar to that hereinbefore described and operates in a similar manner.

Referring to Fig. 8 of the drawings, the embodiment illustrated therein includes stationary and movable cam members and 162 respectively provided with cam surfaces 164 and 166 extending generally transversely of the axis of rotation of the cam 4member 162. The cam surfaces 164 and 166 are respectively provided with squarish cavities 168 and 170 therein for balls 172 and cylindrical rollers 174, respectively. The axes of the rollers 174 make acute angles with the axis of rotation of the movable cam member 162 to provide a centering action in much the same manner as in the embodiment of Fig. 7 of the drawings.

In the embodiment of Fig. 9 of the drawings, stationary and movable cam members and 182 respectively having generally transverse cam surfaces 184 and 186 are provided.v The cam surfaces 184 and 186 are provided with cavities 188 and 190 therein, respectively, these cavities also being squarish in planes parallel to the axis of rotation of the cam member 182. The cavities 188 are contoured to receive wheels 192 with integral roller-like axles, and the cavities 190 are contoured to receive balls. The resulting ball-over-wheel engagement is substantially identical to the ball-over roller engagement hereinbefore discussed in connection with the embodiment of Figs. 1 to 5 of the drawings, the embodiment of Fig. 9 attaining all of the advantages of the embodiment of Figs. 1 to 5. The wheels 192 provide the effect of larger rollers for greater strength, which is an important feature.

Turning now to Fig. l0 of the drawings, the embodiment illustrated therein includes stationary and movable cam members 200 and 202 respectively provided with generally transverse cam surfaces 204 and 206 having cavities Zil and 210 therein, respectively. The cavities 208 and 210 are contoured to receive axled wheels 212 and .214, respectively, and are squarish in cross section in planes parallel to the axis of rotation of the movable cam member 202. The wheels 212 are shown as provided with spherical surfaces, which makes these wheels balls, in effect, to obtain the effect of roller-over-ball engagement between the wheels 214 and 212, while providing greater strength due to the more massive wheels.

212 and 214. The embodiment of Fig. 10 of the drawings operates insubstantially the same way and attainsv substantialiy the same results as the embodiment of Figs. 1 to 5 of the drawings.

In the embodiment of Figs. 11 and l2 of the drawings, the. numerals 220 and 222 respectively designate stationary and movable cam members respectively having generally transverse cam surfaces 224 and 226. The cam surface 224 is provided with flat bottomed cylindrical cavities 228 therein which are squarish in cross section in planes parallel to the axis of rotation of the movable cam member 221) and which contain balls 230. The cam surface 2126 is provided Vwith circumferentially spaced, radially oriented, elongated cavities 232 therein which receive cam elements 234 engageable bythe balls 230.

9 The cam elements 234 are provided with rounded edges engageable by the balls 230 and are provided with rounded edges engageable with the at bottom walls of the cavities 232. Interposed between the sides of the cam elements 234 and the perpendicular side walls of the cavities 232 are layers'236 of a resilient material, such as rubber. With this construction, the cam elements 234 can rock relative to the cam member 222 as they are engaged and disengaged by the balls 230, the resilient layers 236 serving to center the cam elements 234 in their cavities 232 and serving to absorb shocks due to the impact forces resulting from engagement of the balls 230 with the cam elements 234. This shock absorbing action is important in that it tends to further minimize fatigue failures due to metal crystallization, for example. It will be noted that the embodiment of Figs. l1 and 12 of the drawings operates in a manner similar to and attains substantially the same results as the embodiment of Figs. 1 to 5 of the drawings.

Referring now to Fig. 13 of the drawings, illustrated therein is an embodiment which is designed to maintain on-center ball engagement in a ball-over-ball arrangement. More particularly, the embodiment of Fig. 13 includes stationary and movable cam members 240 and 242 respectively having cam surfaces 244 and 246 extending genen ally transversely of the axis of rotation ofthe movable cam member. The cam surface 244 is provided therein with an annular groove 24S inthe bottom of which are formed cylindrical at bottomed cavities 250 for balls 252. The cam surface 246 of the movable cam member 242 is formed by an annular rib 254 on the cam member 242 which extends into the annular groove 248 in the cam member 24d. The annular rib 254 is provided with cavities 256 therein having the form of radial notches in the rib, these notches having flat bottom walls and side walls perpendicular thereto. Balls 258 are disposed in the cavities 256. With this construction, the balls 258 are guided by the sides of the annular groove A243 into oncenter engagement with balls 252 to eliminate any radial loads which would be the result of off-center ball-to-ball engagement, which is an important feature of this embodiment.

Although I have disclosed herein numerous exemplary embodiments of my invention for purposes of illustration, it will be understood that various changes, modications and substitutions may be incorporated in such embodiments without departing from the spirit of the invention as defined in the claims hereinafter appearing.

I claim as my invention:

l. in a rotary hammer, the combination of: two cam members relatively rotatable about and relatively reciprocable along an axis and respectively provided with cam surfaces thereon, said cam surfaces facing each other and extending generally transversely of said axis, each of said cam surfaces being provided therein with circumferentially spaced cavities having substantially hat bottom walls and having side walls substantially perpendicular to said bottom walls, said cavities in one of said cam surfaces being cylindrical and said cavities in the other of said cam surfaces being elongated and radially oriented; balls respectively disposed in and projecting from said cylindrical cavities in said one cam surface; and rollers respectively disposed in and projecting from said elongated cavities in said other earn surface and engageable with said balls in said cylindrical cavities in said one cam surface so as to produce relative reciprocation of said cam members in response to relative rotation thereof.

2. In a rotary hammer, the combination of: two cam members relatively rotatable about and relatively reciprocable along an axis and respectively provided with cam bottom walls, said cavities in one of said cam surfaces be ing cylindrical and said cavities in the other of said cam surfaces being elongated and radially oriented; balls respectively disposed in and projecting from said cylindrical cavities in said one cam surface; and cylindrical rollers respectively disposed in and projecting from said elongated cavities in said other cam surface and engageable with said balls in said cylindrical cavities in said one cam surface so as to produce relative reciprocation of said cam members in response to relative rotation thereof.

3. In a rotary hammer, the combination of: two cam members relatively rotatable about and relatively reciprocable along an axis and respectively provided with cam Surfaces thereon, said cam surfaces facing each other and extending generally transversely of said axis, each of said cam surfaces being provided therein with circumferen- -tially spaced cavities having substantially iiat bottom walls and having side walls substantially perpendicular to said bottom Walls, said cavities in one of said cam surfaces being cylindrical and said cavities in the other of said cam surfaces being elongated and radially oriented; balls respectively disposed in and projecting from said cylindrical cavities in said one cam surface; and rollers respectively disposed in and projecting from said elongated cavities in said other cam surface and engageable with said balls in said cylindrical cavities in said one cam surface so as to produce relative reciprocation of said cam members in response to relative rotation thereof, said rollers projecting from said elongated cavities farther than said balls projectfrom said cylindrical cavities so that said rollers engage said one cam surface intermediate said cylindrical cavities therein when said rollers are out of engagement with said balls.

4. in a rotary hammer, the combination of: a housing providing an axis; a stationary cam member in and carried by said housing and having a cam surface which extends generally transversely of said axis, said cam surface of said stationary cam member being provided with circumferentially spaced cavities therein having substantially at bottom walls and having side walls substantially perpendicular to said bottom walls thereof; a shaft in said housing and extending axially through said stationary cam member, said shaft being rotatable about and reciprocable along said axis; a movable cam member in said housing and fixed on said shaft, said movable cam member having a cam surface which extends generally transversely of said axis and which faces said cam surface of said stationary cam member, said cam surface of said movable cam member being provided with circumferentially spaced cavities therein having substantially tiat bottom walls and having side walls substantially perpendicular to said bottom walls thereof; rotatable cam elements of circular cross Section respectively disposed in and projecting from said cavities in said earn surface of said stationary cam member; and rotatable cam elements of circular cross section respectively disposed in and projecting from said cavities in said cam surface of said movable cam member and en-` gageable with said rotatable cam elements in said cavltiesA in said cam surface of said stationary cam member so as to produce reciprocatory movement of said movable cam member and said shaft in response to rotation thereof.

5. A rotary hammer as defined in claim 4 wherein said movable cam member is provided with lubricant scoop-gx ing ports extending from the periphery of said movablecam member to said cavities in said cam surface thereof, said lubricant sooo-ping ports facing in the direction of circumferential movement of the periphery of said movable cam member so that they deliver a lubricant Within Said housing to said rotatable cam elements inresponsexto .rotation of said shaft and said movable cam member.

' 6. 'In a--ro-tary hammer, the combination of: a housing having an'axis;l a stationary cam member in and carried by said housing and having a cam surface which extends generally transversehl of said axis; a shaft in said housing, said shaft being rotatable about and reciprocable along said axis; a movable cam member in said housing and fixed on said shaft, said movable cam member having a cam surface which extends generally transversely of said axis and which faces said cam surface of said stationary cam member, said cam surface of said movable cam member being provided with circumferentially spaced cavities therein, said movable cam member being provided with lubricant scooping ports which extend from the periphery thereof inwardly to said cavities, said lubricant scooping ports facing in the direction of circumferential movement of the periphery of said movable cam member in response to rotation of said shaft and said movable cam member soas to scoop Ia lubricant in said housing into said cavities; circumferentially spaced cam elements projecting from said cam surface of said stationary cam member; and rotatable cam elements of circular cross section respectively disposed in and projecting from said cavities in said cam surface of said movable cam member and engageable with said cam elements projecting from said cam surface of said stationary earn member so as to produce reciprocatory movement of said movable cam member in respense to rotation of said shaft and said movable cam member.

7. A rotary hammer as defined in claim 4 wherein said shaft is hollow and communicates .with the interior of said housing at two axially spaced points, said rotary hammer including lubricant pumping means in said hollow shaft between said points and operating in response to reciprocatory movement of said shaft for circulating lubricant through said shaft and said housing.

8. In a rotary hammer, the combination of: a housing :providing an axis; a stationary cam member in and carried by said housing; a hollow shaft in and carried by said housing and extending axially through said stationary cam member, said hollow shaft being rotatable about and reciprocable along said axis and communicating with the interior of said housing at axially spaced points; inertia pumping means in and carried by said hollow shaft between said points and operating in response to reciprocatory movement of said shaft for pumping lubricant through said shaft and said housing; a movable cam member in said housing and fixed on said shaft; means for rotating said shaft; and interengageable cam elements on said cam members for reciprocating said movable cam member and said shaft in response to rotation thereof.

9. A rotary hammer as defined in claim 4 including two bearings carried by said housing and surrounding and engaging said shaft, said bearings being located on opposite sides of said stationary and movable cam members.

t0. ln a rotary hammer, the combination of: a housing providing an axis; a stationary cam member in and carried by said housing; a shaft in said housing and extending axially through said stationary cam member, said shaft being rotatable about and reciprocable along said axis; a movable cam member in said housing and fixed on said shaft adjacent said stationary cam member; means for rotating said shaft; interengageable cam elements on said stationary and movable cam members for reciproeating said movable cam member upon rotation of said shaft and said movable cam member; and two bearings respectively carried by said housing on opposite sides of said stationary and movable cam members, said bearings surrounding and engaging said shaft.

l1. in a rotary hammer, the combination of: a stationary cam member; a movable cam member adjacent said stationary cam member; interengageable elements on said cam members fer reciprocating said movable cam member relative to said stationary cam member in response to rotation of said movable oammember relative to said stationary cam member; a shaft carrying said movable cam member and extending through said stationary cam member; a journal bearing surrounding and engagingisaid shaft on one side of said stationary and movable cam members; another journal bearing surrounding and engaging said shaft on the opposite-side of said stationary and movable cam members; and a housing enclosing said stationary and movable cam members and atleastv a portion of said shaft and supporting said journal bearings.

1,2.l A rotary hammer according to claim 1l wherein said shaft includes two parts respectively threaded into opposite sides of said movable cam member.

13. A rotary hammer as defined in claim ll including a drive shaft telescopically related to the shaft first mentioned, and including a floating drive pin extending through a transverse opening in one of said shafts into longitudinal grooves in the other.

'14. in a rotary hammer, the combination of: ahousing; a stationary cam member in and carried by said housing; a movable cam member in said housing adjacent said stationary cam member, said movable cam member being rotatable and reciprocable relative to said stationary cam member; a shaft connected to said movable cam member and rotatable and reciprocable relative to said stationary cam member; bearing means for said shaft carried by said housing and interposed between said shaft and said housing; a drive shaft telescopically related to the shaft first mentioned, one of said shafts having a transverse opening therein and the other having longitudinal grooves therein registering with said opening; and a floating drive pin extending through said opening and into said longitudinal grooves to transmit rotation of said drive shaft to said first-mentioned shaft while permitting reciprocatory motion of the latter relative to said stationary cam member.

15. In a rotary hammer, the combination of: an internally threaded barrel; a stationary cam member threaded into said barrel intermediate the ends thereof; a movable cam member in said barrel adjacent said stationary cam member, said movable cam member being rotatable and reciprocable relative to said stationary cam member; a shaft rotatable and reciprocable relative to said stationary cam member and extending axially through said stationary cam member, said movable cam member being fixed on said shaft; interengageable cam elements on said stationary and movable cam members for reciprocating said movable cam member and said shaft upon rotation thereof; heads threaded into the ends of said barrel on opposite sides, respectively, of said stationary and movable cam members; and bearings carried by said heads and surrounding and engaging said shaft on opposite sides, respectively, of said stationary and movable cam members.

16. A rotary hammer according to claim l5 including a drive shaft telescopically related to the shaft first mentioned, one of said shafts having a transverse opening therein and the other having longitudinal grooves aligned with said opening, said hammer including a lioating drive pin extending through said opening into said grooves to transmit rotation from said drive shaft to said first-mentioned shaft while permitting reciprocatory movement or said first-mentioned shaft.

17. ln a rotary hammer, the combination of: a housing providing an axis; a stationary cam member in and carried by said housing; means in said housing providing a movable cam member adjacent said stationary cam member and a shaft connected to said movable cam member, said movable cam member and said shaft being rotatable about and reciprocable along said axis; interengageable cam elements on said stationary and movable cam members for reciprocating said movable cam member and said shaft upon rotation of said shaft and said movable cam memberga Abearingsurrounding and engagingsaid shaft and carried by said housing on one side of said stationary and movable cam members; a drive shaft extending through said stationary cam member into said means; a connection between said drive shaft and said means, said connection including a floating drive pin extending through a transverse opening in said drive shaft into longitudinal grooves in said means; and another bearing carried by said housing on the opposite side of said stationary and movable cam members from the first bearing 5 mentioned and surrounding said drive shaft.

18. A rotary hammer as defined in claim 17 wherein said other bearing engages the irst shaft mentioned.

19. A rotary hammer as set forth in claim 17 wherein said movable and stationary cam members respectively 10 have movable and stationary cam surfaces facing each other and each provided with circumferentially spaced cavities having substantially at bottom walls and-having side Walls substantially perpendicular to said bottom walls, said interengageable cam elements including rotat- 15 able cam elements of circular cross section respectively disposed in and projecting from said cavities in said cam surfaces.

References Cited in the le of this patent UNTED STATES P TENTS 

